Reference Guide on DNA Evidence

David H. Regents' Professor, Arizona State University College of Law
Fellow, Center for the Study of Law, Science, and Technology

George F. Sensabaugh, Jr.
Professor, School of Public Health, University of California at Berkeley

Note: This monograph appears in the Reference Guide on Scientific Evidence (Federal Judicial Center ed. 2d ed., 2000). It can be downloaded from the Federal Judicial Center's website at

I. Introduction A. Summary of Contents
B. Objections to DNA Evidence
C. Relevant Expertise
II. Overview of Variation in DNA and Its Detection A. DNA, Chromosomes, Sex, and Genes
B. Types of Polymorphisms and Methods of Detection
III. DNA Profiling with Loci Having Discrete Alleles A. DNA Extraction and Amplification
B. DNA Analysis
IV. VNTR Profiling A. Validity of the Underlying Scientific Theory
B. Validity and Reliability of the Laboratory Techniques
V. Sample Quantity and Quality A. Did the Sample Contain Enough DNA?
B. Was the Sample of Sufficient Quality?
C. Does a Sample Contain DNA from More than One Person?
VI. Laboratory Performance A. Quality Control and Assurance
B. Handling Samples
VII. Interpretation of Laboratory Results A. Exclusions, Inclusions, and Inconclusive Results
B. Alternative Hypotheses
1. Error
2. Kinship
3. Coincidence

C. Measures of Probative Value
1. Likelihood Ratios
2. Posterior Probabilities

D. Which Probabilities or Statistics Should Be Presented?
1. Should Match Probabilities Be Excluded?
2. Should Likelihood Ratios be Excluded?
3. Should Posterior Probabilities be Excluded?

E. Which Verbal Expressions of Probative Value Should Be Presented?
VIII. Novel Applications of DNA Technology A. Is the Application Novel?
B. Is the Underlying Scientific Theory Valid?
C. Has the Probability of a Chance Match Been Estimated Correctly?
1. How Was the Database Obtained?
2. How Large is the Sampling Error?
3. How Was the Random Match Probability Computed?

D. What Is the Relevant Scientific Community?
Appendix A. Structure of DNA
B. DNA Probes
C. Examples of Genetic Markers in Forensic Identification
D. Steps of PCR Amplification
E. Quantities of DNA in Forensic Samples